1. Field of the Invention
The present invention relates to an apparatus or assembly for connecting a valve element to a valve stem and, more particularly, to an apparatus for connecting the stem or shaft of a butterfly valve to the disk.
2. Description of the Prior Art
Valves employing pivotable closure elements, such as butterfly valves, are widely used in the industry for fluid handling and control. In a typical butterfly valve assembly, the disk of valve element is pivotally mounted in the flow passage of the valve body. To pivotally mount the disk in the valve so as to be able to selectively open and close the valve, it is common to use one or more stems or shafts which extend through the valve body into the flow passage and which are fixed to the disk so that rotation of the shaft or shafts results in rotation of the disk.
It is the practice in disk or butterfly valve assemblies to secure the stem to the disk by means of pins which fit in registering holes in the stem and a hub of the disk such that the disk and stem are keyed to one another. Alternately, it is common to thread the bore extending through the valve stem and use a threaded bolt which extends through a registering bore in a hub of the disk, the threaded bolt engaging the threaded bore in the stem to secure the disk to the stem. In such assemblies, because of machining tolerances and to permit fit, the bolt or pin does not frictionally engage both the core in the hub of the disk and the registering bore in the stem. The result is that bending moment if a force is applied to the disk/stem assembly, such as, for example, when the stem is rotated to position the disk in the valve.